In-vehicle antenna apparatus

Abstract

 Rear glass is provided with a patch-like radiation conductor and a first ground conductor surrounding the patch-like radiation conductor. An electronic circuit unit includes a base plate fixed on the rear glass; a frame body which houses a circuit substrate and is fixed on the base plate; and a cover for covering the frame body. One surface of the circuit substrate defines a component-holding surface which is connected with a second end of a feeder cable connected with the radiation conductor and the first ground conductor. The other surface of the circuit substrate is provided with a second ground conductor so as to function as a radio-wave reflective surface. The radio-wave reflective surface faces the radiation conductor and the first ground conductor disposed on the rear glass in a manner such that the radio-wave reflective surface is separated from the radiation conductor and the first ground conductor by a predetermined distance.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The present invention relates to an in-vehicle antenna apparatus mounted on a windowpane of a vehicle, such as an automobile, and particularly, to an in-vehicle antenna apparatus provided with a patch-like radiation conductor disposed on an inner surface of a windowpane.

2. Description of the Related Art

[0002] Japanese Unexamined Patent Application Publication No. 2002-252520 (p. 3 to p. 5, Fig. 1) discloses an example of a conventional in-vehicle antenna apparatus provided with a radiation conductor and a ground conductor disposed on an inner surface of rear glass or front glass of a vehicle. The radiation conductor and the ground conductor are connected to a circuit substrate via a coaxial cable such that the in-vehicle antenna apparatus is capable of, for example, receiving a circularly-polarized wave or a linearly-polarized wave sent from a satellite or a ground-based station. The radiation conductor has a patch-like structure, and an electric feeding point of the radiation conductor is connected with a central conductor of the coaxial cable. On the other hand, the ground conductor has a frame-like structure that surrounds the radiation conductor, and is separated from the radiation conductor by a predetermined distance. The ground conductor is connected with an outer conductor of the coaxial cable.

[0003] In an in-vehicle antenna apparatus of this type, an electronic circuit unit is attached to the inner surface of a sheet of glass, such as rear glass or front glass, facing the inside of the vehicle. This electronic circuit unit contains the circuit substrate which is electrically connected with the radiation conductor and the ground conductor disposed on the sheet of glass. This allows for the radiation conductor to receive electricity and load a received signal. In comparison with other types of antenna apparatuses that are set on the exterior of a vehicle, such as a roof, this type of antenna apparatus is advantageous in having a longer lifespan and a lower possibility of being stolen. Furthermore, in comparison with antenna apparatuses that are set in the vicinity of the inner surface of a windowpane of a vehicle, this type of antenna apparatus is advantageous in providing a good space factor and a wide angle of view.

[0004] In such a conventional in-vehicle antenna apparatus, however, the ground conductor surrounding the radiation conductor must be given at least a certain surface area in order to prevent the directional characteristics from deteriorating. This means that a ground conductor with a large dimension must be provided on the sheet of glass, such as rear glass or front glass, and is thus problematic in that such a large-size ground conductor may narrow the angle of view for vehicle occupants including a driver.

[0005] Furthermore, in this example of a conventional in-vehicle antenna apparatus, which is a flat patch antenna type having the radiation conductor and the ground conductor disposed on the inner surface of the sheet of glass, a radiation pattern (main lobe) mainly forms on the exterior of the sheet of glass. However, the antenna apparatus has directional characteristics in which a radiation pattern also forms slightly in the interior of the sheet of glass. This weakens the directional characteristics for intensely emitting radio-waves outward from the sheet of glass, and is thus problematic in that the radiation gain in the incoming direction of a tuned radio-wave becomes lower.

SUMMARY OF THE INVENTION

[0006] Accordingly, it is an object of the present invention to provide an in-vehicle antenna apparatus that is compact in size and that achieves a high radiation gain.

[0007] In order to achieve the aforementioned object, the present invention provides an in-vehicle antenna apparatus which includes a sheet of glass serving as a windowpane installed in a vehicle; a patch-like radiation conductor disposed on an inner surface of the sheet of glass facing an inside of the vehicle; and a circuit substrate whose first surface is provided with an electric circuit connected to the radiation conductor. A second surface of the circuit substrate is provided with a second ground conductor for the electric circuit, the second ground conductor being opposed to and disposed separate from the radiation conductor and functioning as a radio-wave reflective surface.

[0008] Accordingly, due to the fact that the second ground conductor on the second surface of the circuit substrate is opposed to and disposed separate from the patch-like radiation conductor on the inner surface of the sheet of glass so as to function as the radio-wave reflective surface, the second ground conductor for the electric circuit can also function as a ground conductor for the radiation conductor. This contributes to a size reduction of the in-vehicle antenna apparatus, and moreover, achieves a higher radiation gain in the incoming direction of a tuned radio-wave due to the radio-wave reflective surface.

[0009] Furthermore, in the in-vehicle antenna apparatus, although the second ground conductor in the circuit substrate may serve entirely as a ground conductor for the radiation conductor, the inner surface of the sheet of glass is preferably provided with a first frame-like ground conductor that surrounds the radiation conductor. In this case, the electric circuit is preferably connected with the radiation conductor and the first ground conductor, and the second ground conductor is preferably opposed to and disposed separate from the radiation conductor and the first ground conductor so as to function as the radio-wave reflective surface. In other words, since the second ground conductor on the second surface of the circuit substrate also functions as a part of the first ground conductor, at least a certain surface area required for the overall ground conductor can be attained by the total dimension of the second ground conductor and the first ground conductor disposed on the sheet of glass. Consequently, this contributes to a size reduction of the first ground conductor disposed on the inner surface of the sheet of glass.

[0010] Furthermore, the in-vehicle antenna apparatus may further include a base plate fixed on the inner surface of the sheet of glass; and a housing that houses the circuit substrate. The housing is preferably mounted on the inner surface of the sheet of glass via the base plate. According to this structure, since the housing can be easily attached to and detached from the sheet of glass, it is not necessary to perform complicated processes, such as demounting and remounting processes, when the circuit substrate is to be inspected or replaced with a new one. In this case, the housing preferably includes a sheet-metal frame body that surrounds and supports the circuit substrate and that is fixed to the base plate in a detachable manner; and a sheet-metal cover that engages with the frame body so as to cover the first surface of the circuit substrate. Accordingly, since the circuit substrate can be readily installed in the frame body before the engagement process of the cover, the overall assembly process is simplified.

[0011] According to the in-vehicle antenna apparatus of the present invention, the patch-like radiation conductor on the inner surface of the sheet of glass is connected with the electric circuit on the first surface of the circuit substrate, and the second ground conductor on the second surface of the circuit substrate is opposed to and disposed separate from the radiation conductor so as to function as the radio-wave reflective surface. Thus, the second ground conductor for the electric circuit on the circuit substrate functions both as a part of the first ground conductor for the radiation conductor and as the radio-wave reflective surface for improving the radiation gain in the incoming direction of a tuned radio-wave. Accordingly, an in-vehicle antenna apparatus that is compact in size and that achieves a high radiation gain is achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] 

Figs. 1A and 1B are schematic diagrams illustrating a mounting position of an in-vehicle antenna apparatus according to an embodiment of the present invention;

Fig. 2 is a perspective view of an electronic circuit unit of a ground-based antenna device included in the in-vehicle antenna apparatus;

Fig. 3 is a schematic view illustrating a positional relationship between a base plate of the electronic circuit unit shown in Fig. 2 and a radiation conductor;

Fig. 4 is an exploded perspective view of the electronic circuit unit shown in Fig. 2;

Fig. 5 is a plan view of the electronic circuit unit shown in Fig. 2;

Fig. 6 is a bottom view of the electronic circuit unit shown in Fig. 2;

Fig. 7 is a side view of the electronic circuit unit shown in Fig. 2;

Fig. 8 is another side view of the electronic circuit unit in Fig. 2 as viewed from a side different from the side shown in Fig. 7;

Fig. 9 is a perspective view of a satellite antenna device included in the in-vehicle antenna apparatus;

Fig. 10 is a schematic view illustrating a positional relationship between a base plate of an electronic circuit unit shown in Fig. 9 and a radiation conductor;

Fig. 11 is an exploded perspective view of the electronic circuit unit shown in Fig. 9;

Fig. 12 is a plan view of the electronic circuit unit shown in Fig. 9;

Fig. 13 is a bottom view of the electronic circuit unit shown in Fig. 9;

Fig. 14 is a side view of the electronic circuit unit shown in Fig. 9; and

Fig. 15 is another side view of the electronic circuit unit in Fig. 9 as viewed from a side different from the side shown in Fig. 14.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Embodiments of the present invention will now be described with reference to the drawings. Figs. 1A and 1B are schematic views illustrating a mounting position of an in-vehicle antenna apparatus according to an embodiment of the present invention. Specifically, Fig. 1A is a side view of a vehicle, and Fig. 1B is a front view of rear glass as viewed from the inside of the vehicle. Figs. 2 to 8 illustrate a ground-based antenna device 100 included the in-vehicle antenna apparatus. Fig. 2 is a perspective view of an electronic circuit unit 1 provided in the ground-based antenna device 100. Fig. 3 is a schematic view illustrating a positional relationship between a base plate 4 of the electronic circuit unit 1 and a radiation conductor 2. Fig. 4 is an exploded perspective view of the electronic circuit unit 1. Fig. 5 is a plan view of the electronic circuit unit 1. Fig. 6 is a bottom view of the electronic circuit unit 1. Fig. 7 is a side view of the electronic circuit unit 1. Fig. 8 is another side view of the electronic circuit unit 1 as viewed from a side different from the side shown in Fig. 7. In Fig. 8, a coaxial feeder cable 5 and a connector cover 12 are not shown. On the other hand, Figs. 9 to 15 illustrate a satellite antenna device 200 included in the in-vehicle antenna apparatus. Specifically, Fig. 9 is a perspective view of an electronic circuit unit 21 provided in the satellite antenna device 200. Fig. 10 is a schematic view illustrating a positional relationship between a base plate 24 of the electronic circuit unit 21 and a radiation conductor 22. Fig. 11 is an exploded perspective view of the electronic circuit unit 21. Fig. 12 is a plan view of the electronic circuit unit 21. Fig. 13 is a bottom view of the electronic circuit unit 21. Fig. 14 is a side view of the electronic circuit unit 21. Fig. 15 is another side view of the electronic circuit unit 21 as viewed from a side different from the side shown in Fig. 14.

[0014] Referring to Figs. 1A and 1B, the in-vehicle antenna apparatus according to this embodiment includes the ground-based antenna device 100 and the satellite antenna device 200 which are arranged substantially in a side-by-side manner on an inner surface of rear glass 51 facing the inside of a vehicle 50. The ground-based antenna device 100 is capable of receiving a linearly-polarized wave (i.e. a vertically polarized wave) sent from a ground-based station, whereas the satellite antenna device 200 is capable of receiving a circularly-polarized wave sent from a satellite. The in-vehicle antenna apparatus operates the ground-based antenna device 100 and the satellite antenna device 200 in a mutually complementary manner so as to constantly achieve a good reception.

[0015] The ground-based antenna device 100 will first be described with reference to Figs. 2 to 8. The ground-based antenna device 100 is a slot antenna device and mainly includes the electronic circuit unit 1 attached to the inner surface of the rear glass 51 facing the inside of the vehicle 50, and the radiation conductor 2 disposed on the inner surface of the rear glass 51. The electronic circuit unit 1 includes the base plate 4 formed of a sheet metal, which is fixed on the inner surface of the rear glass 51 and is provided with a projecting reflector plate 3; a circuit substrate 6 electrically connected with the radiation conductor 2 via the coaxial feeder cable 5; a sheet-metal housing 7 that houses the circuit substrate 6 and is attached to the base plate 4; a coaxial cable (output cable) 8 whose first end is connected to the circuit substrate 6 and whose second end is connected to an external receiving unit (not shown); and a DC cable 9 for power supply.

[0016] The housing 7 includes a sheet-metal frame-body 10 that surrounds and supports the circuit substrate 6; a sheet-metal cover 11 that is engaged with the frame body 10 so as to cover the circuit substrate 6; and a sheet-metal connector-cover 12 for covering an opening 11a of the cover 11. Two projecting sections of the frame body 10, namely, two projection tabs 10a, are fixed to the base plate 4 via setscrews 13. In the electronic circuit unit 1 of the ground-based antenna device 100, the housing 7 is attached to the base plate 4 in a detachable manner, and the base plate 4 is securely fixed to the rear glass 51 with moisture curing resin 14 (see Fig. 3).

[0017] Each component of the ground-based antenna device 100 will be described in detail. The radiation conductor 2 is a conductor layer composed of highly-conductive metal, such as Ag. Referring to Fig. 3, the radiation conductor 2 is provided with a slot 2a having a predetermined dimension. Two segments of the radiation conductor 2 at opposite sides of the slot 2a function as electric feeding points connected with a first end portion of the feeder cable 5. Moreover, referring to the bottom view of Fig. 6, three sections of the radiation conductor 2 are soldered to corresponding soldering sections 4a of the base plate 4, such that the base plate 4 electrically functions as a ground.

[0018] The reflector plate 3 is a rectangular metal plate that extends from the base plate 4 at an angle and that faces the radiation conductor 2. The reflector plate 3 is used for reflecting radio-waves and thus contributes to achieving a higher gain at low elevation angles. A back surface of the reflector plate 3 is provided with an angle-maintaining member 15 which is fixed to the reflector plate 3 and a section of the base plate 4 adjacent to the reflector plate 3 in a caulked manner. The angle-maintaining member 15 is formed by punching a metal plate into a predetermined shape and then bending the metal plate, and is provided with a pair of contact edges 15a for setting the positional relationship between the back surface of the reflector plate 3 and a flat surface of the base plate 4 in a relatively desired manner. Specifically, the contact edges 15a extend from the flat surface of the base plate 4 and along the back surface of the reflector plate 3, and are lines that are cut with high dimensional accuracy during the punching process of the angle-maintaining member 15. Due to the fact that the pair of contact edges 15a with high dimensional accuracy abuts on the flat surface of the base plate 4 and the back surface of the reflector plate 3, the angle of inclination of the reflector plate 3 can be set in a highly accurate manner with respect to the base plate 4. Furthermore, the angle-maintaining member 15 is also provided with a pair of erect portions 15b which face each other and extend along the respective contact edges 15a. The erect portions 15b are formed by bending two opposite segments of the metal plate at a substantially right angle in a direction in which the two contact edges 15a are opposed to each other. The angle-maintaining member 15 increases the mechanical strength of the reflector plate 3 and thus prevents undesired deformation of the reflector plate 3.

[0019] In addition to the three soldering sections 4a, the base plate 4 is also provided with two internal-thread portions 4b. Furthermore, referring to Fig. 6, the central part of each soldering section 4a is provided with a semispherical protrusion 4c that protrudes towards the radiation conductor 2. Each of the protrusions 4c abuts on the radiation conductor 2 such that a solder-accumulation space is formed around the protrusion 4c. Moreover, the peripheries of the soldering sections 4a are correspondingly provided with cutout sections 4d each having, for example, an L-shape, I-shape, or circular shape. This forms narrow sections 4e that connect the soldering sections 4a and other sections of the base plate 4. Accordingly, during a heating process for soldering the soldering sections 4a to the radiation conductor 2, the heat applied is less likely to be transmitted to the other undesired sections, whereby the soldering process can be performed efficiently in a small amount of time.

[0020] Furthermore, the base plate 4 is also provided with a plurality of height-adjustment portions 4f at positions distant from the soldering sections 4a such that these height-adjustment portions 4f protrude towards the rear glass 51. The height-adjustment portions 4f have a semispherical shape with substantially the same dimension as the protrusions 4c. Consequently, the base plate 4 faces the rear glass 51 in a point-contact fashion, thereby ensuring the protrusions 4c of the soldering sections 4a to abut on the radiation conductor 2 during the attachment process of the base plate 4. This prevents undesirable rising of the base plate 4. Referring to Fig. 3, in a state where the base plate 4 is fixed to the rear glass 51 via the moisture curing resin 14, the soldering sections 4a are soldered to the radiation conductor 2 during the attachment process of the base plate 4. Therefore, it is not necessary to temporarily fix the base plate 4 using, for example, a double-side adhesive tape while waiting for the moisture curing resin 14 to harden.

[0021] Furthermore, referring to Figs. 3, 4, and 6, the base plate 4 is provided with a pair of supporting segments 4g projected towards the interior of the frame body 10. In a state where the base plate 4 is fixed to the rear glass 51, the pair of supporting segments 4g faces the rear glass 51 and are separated from the rear glass 51 by a predetermined distance. This allows the feeder cable 5 to be sandwiched between the rear glass 51 and the supporting segments 4g so as to achieve proper positioning of the feeder cable 5. Moreover, the base plate 4 is further provided with a hook segment 4h which protrudes outward of the frame body 10. In a state where the base plate 4 is fixed to the rear glass 51, the hook segment 4h is separated from the rear glass 51 by a distance much greater than the distance separating the supporting segments 4g from the rear glass 51. Consequently, the feeder cable 5 extending towards the exterior of the frame body 10 can be hooked to the hook segment 4h, thereby achieving proper positioning of the feeder cable 5.

[0022] The first end portion of the feeder cable 5 soldered to the electric feeding points of the radiation conductor 2 extends parallel to the inner surface of the rear glass 51 towards the exterior of the frame body 10. Since this parallel-extending portion of the feeder cable 5 is positioned by the pair of supporting segments 4g and the rear glass 51 by being sandwiched therebetween, this portion of the feeder cable 5 above the rear glass 51 can extend efficiently along a predetermined path. On the other hand, since the feeder cable 5 extending outward from the frame body 10 can be positioned readily by hooking the feeder cable 5 onto the hook segment 4h, the feeder cable 5 can also extend efficiently adjacent to the exterior of the frame body 10. Referring to Fig. 4, a second end portion of the feeder cable 5 has a connector 16 attached thereto. The connector 16 is connected with a connector 17 disposed on the circuit substrate 6 and facing the opening 11a of the cover 11, such that the second end portion of the feeder cable 5 is connected with an input section of a pre-amplifying circuit.

[0023] As shown in Fig. 4, the frame body 10 mainly includes a pair of side walls 10b, 10c facing each other, and a pair of side walls 10d, 10e facing each other. Each of the side walls 10d, 10e is provided with one of the projection tabs 10a which are louver tabs. The side wall 10d is provided with an arm segment 10f extending outward from one longitudinal end of the side wall 10d. Referring to Fig. 7, the frame body 10 includes a large-dimension body part 10A which is adjacent to the cover 11 and is shown at an upper side of the drawing. The large-dimension body part 10A has a dimension larger than that of a body part adjacent to the base plate 4, which is shown at a lower side of the drawing. Specifically, one longitudinal side of each of the side walls 10d, 10e is given a bulging segment, and the side wall 10c is bent in a staircase manner. Thus, an opening of the frame body 10 adjacent to the cover 11 is given a larger dimension, such that one side of the large-dimension body part 10A bulges towards the reflector plate 3. In view of the fact that the circuit substrate 6 is housed in the large-dimension body part 10A, a sufficiently large installation space for the circuit substrate 6 can be obtained in the frame body 10 without increasing the overall size of the frame body 10 and also without positioning a section of the frame body 10 in a region where the frame body 10 could possibly interfere with the operation of the reflector plate 3. Furthermore, in the large-dimension body part 10A, the side walls 10b to 10e are each provided with a plurality of small holes 10h (see Fig. 4).

[0024] By fastening the setscrews 13 extending through the corresponding projection tabs 10a to the corresponding internal-thread portions 4b, the frame body 10 is secured to the base plate 4 preliminarily fixed on the rear glass 51. Referring to Fig. 1A, the rear glass 51 is a windowpane installed in the vehicle 50 at an angle with respect to the ground. When the frame body 10 is fixed to the rear glass 51 via the base plate 4, the side wall 10b defines a lower region disposed closer to the ground. Consequently, referring to Fig. 8, the side wall 10b is provided with two circular drainage holes 10i which allow an internal space defined by the base plate 4, the rear glass 51, the frame body 10, and the undersurface of the circuit substrate 6 to communicate with the external space. Specifically, the drainage holes 10i allow water droplets entering the internal space to be drained outward quickly so as to prevent water from accumulating in the internal space. Furthermore, the side wall 10b of the frame body 10 is also provided with a clearance recess 10j at a position adjacent to the hook segment 4h of the base plate 4 so that the feeder cable 5 can extend outward.

[0025] The arm segment 10f extending from the side wall 10d of the frame body 10 is provided for holding the coaxial cable 8. The arm segment 10f is provided with a cutout notch 10g whose opening side is relatively narrower. By press-fitting a heat shrinkable tube 18 wrapped around the coaxial cable 8 into the cutout notch 10g, the coaxial cable 8 can be engaged to the arm segment 10f in a single-step fashion, and moreover, the inner conductor and the outer conductor of the coaxial cable 8 can be securely protected. Accordingly, this achieves a stable orientation of the coaxial cable 8 during the assembly process, and also prevents the connecting section of the coaxial cable 8 from being damaged in a case where a pulling force acts upon the coaxial cable 8. Furthermore, by changing the metallic arm segment 10f into a desired shape, the orientation of the coaxial cable 8 can be readily corrected.

[0026] Referring to Fig. 4, one surface of the circuit substrate 6 defines a component-holding surface 6a on which various types of electronic components (not shown) are mounted. Via the connectors 16 and 17, the component-holding surface 6a is connected to the second end portion of the feeder cable 5, whose first end portion is connected with the radiation conductor 2. In other words, the second end portion of the feeder cable 5 is connected with the input section of the pre-amplifying circuit. Furthermore, the component-holding surface 6a has one end of each of the coaxial cable 8 and the DC cable 9 soldered thereto. The other end of the coaxial cable 8 has a connector 19 attached thereto. The peripheral regions of the other surface (undersurface) of the circuit substrate 6 and the component-holding surface 6a are provided with a ground conductor (not shown). Multiple peripheral sections of the component-holding surface 6a are soldered to the frame body 10. Accordingly, the frame body 10 electrically functions as a ground, and moreover, the circuit substrate 6 and the frame body 10 are mechanically joined with each other.

[0027] The cover 11 is provided with the opening 11a which is to be covered by the connector cover 12. Since the connector 17 faces the opening 11a, the connector 16 of the feeder cable 5 can be connected to the connector 17 of the circuit substrate 6 in a state where the frame body 10 holding the circuit substrate 6 is capped with the cover 11. The cover 11 is provided with bent segments 11b substantially around the entire peripheral region of the cover 11. The bent segments 11b fit around the side walls 10b to 10e of the frame body 10 and are provided with a plurality of engagement protrusions 11c that protrude inward. The engagement protrusions 11c are provided at positions corresponding to the small holes 10h of the frame body 10. The resilience of the bent segments 11b allows the engagement protrusions 11c to be press-fitted into the corresponding small holes 10h. Consequently, the cover 11 can be readily engaged to the frame body 10 in a snap-fit fashion. Since the circuit substrate 6 is installed in the frame body 10 before the engagement process of the cover 11, the installation process of the circuit substrate 6 is simplified.

[0028] Referring to Fig. 8, the cover 11 is further provided with a supporting notch 11e in one of the bent segments 11b proximate the opening 11a. The supporting notch 11e is provided for holding the end portion of the feeder cable 5 proximate the connector 16 so as to achieve proper positioning of the feeder cable 5. Thus, the feeder cable 5 extending outward via the hook segment 4h can be readily and properly positioned in the opening 11a. Moreover, since the opening side of the supporting notch 11e is closed when the connector cover 12 is attached to the cover 11, the feeder cable 5 is prevented from being disengaged from the supporting notch 11e.

[0029] When the frame body 10 capped with the cover 11 is fixed to the rear glass 51 via the base plate 4, a region of the cover 11 proximate the side wall 10b of the frame body 10 defines a lower region disposed closer to the ground. Consequently, the lower region of the cover 11 is provided with two rectangular drainage holes 11d. The drainage holes 11d allow water droplets entering an internal space defined by the component-holding surface 6a of the circuit substrate 6, the frame body 10, the cover 11, and the connector cover 12 to be drained outward quickly so as to prevent water from accumulating in the internal space.

[0030] An assembly process of the ground-based antenna device 100 described above will now be described. Firstly, the radiation conductor 2 is formed on an inner surface of a sheet of glass constituting the rear glass 51. Subsequently, the first end portion of the feeder cable 5 is soldered to the electric feeding points of the radiation conductor 2, and the soldering sections 4a of the base plate 4 are soldered to predetermined positions of the radiation conductor 2. In this case, the first end portion of the feeder cable 5 is positioned by the supporting segments 4g of the base plate 4 and the sheet of glass by being sandwiched therebetween. Moreover, the moisture curing resin 14 is preliminarily applied to the bottom surface of the base plate 4. Secondly, the frame body 10 is fixed to the internal-thread portions 4b of the base plate 4 via the setscrews 13. Here, the circuit substrate 6 is preliminarily installed in the frame body 10; the ends of the coaxial cable 8 and the DC cable 9 are preliminarily soldered on the circuit substrate 6; and the cover 11 is preliminarily engaged with the frame body 10. Moreover, when the frame body 10 is to be screwed onto the base plate 4, the feeder cable 5 is pulled toward the exterior of the frame body 10 via the clearance recess 10j of the side wall 10b. Thirdly, after fixing the frame body 10 to the base plate 4, the feeder cable 5 hooked on the hook segment 4h is pulled into the opening 11a of the cover 11 via the supporting notch 11e. Fourthly, the connector 16 attached to the second end portion of the feeder cable 5 is connected to the connector 17 of the circuit substrate 6 facing the opening 11a. Subsequently, the connector cover 12 is mounted on the cover 11 so as to cover the opening 11a, whereby an attachment process for attaching the electronic circuit unit 1 to the sheet of glass constituting the rear glass 51 is completed.

[0031] The satellite antenna device 200 will now be described. The satellite antenna device 200 is a patch antenna device and mainly includes the electronic circuit unit 21 attached to the inner surface of the rear glass 51 facing the inside of the vehicle 50, and the radiation conductor 22 and a first ground conductor 23 disposed on the inner surface of the rear glass 51. The electronic circuit unit 21 includes the base plate 24 formed of a sheet metal, which is fixed on the inner surface of the rear glass 51; a circuit substrate 26 electrically connected with the radiation conductor 22 and the first ground conductor 23 via a coaxial feeder cable 25; a sheet-metal housing 27 that houses the circuit substrate 26 and is attached to the base plate 24; a coaxial cable (input-output cable) 28 whose first end is connected to the circuit substrate 26 and whose second end is connected to an external receiving unit (not shown); and the DC cable 9 for supplying the ground-based antenna device 100 with power.

[0032] The housing 27 includes a sheet-metal rectangular frame body 30 that surrounds and supports the circuit substrate 26; a sheet-metal cover 31 that is engaged with the frame body 30 so as to cover the circuit substrate 26; and a sheet-metal connector cover 32 for covering an opening 31a of the cover 31. Multiple sections of the frame body 30 are fixed to the base plate 24 via setscrews 33. In the electronic circuit unit 21 of the satellite antenna device 200, the housing 27 is attached to the base plate 24 in a detachable manner, and the base plate 24 is securely fixed to the rear glass 51 with moisture curing resin 34 (see Fig. 10).

[0033] Each component of the satellite antenna device 200 will be described in detail. Referring to Fig. 10, the radiation conductor 22 is a substantially rectangular patch electrode whose opposite corners with respect to a diagonal line are provided with cutout degeneracy-splitting elements 22a. On the other hand, the first ground conductor 23 is a frame-like ground electrode that surrounds the radiation conductor 22 in a manner such that the first ground conductor 23 and the radiation conductor 22 are separated by a predetermined distance. The radiation conductor 22 and the first ground conductor 23 are conductor layers composed of highly-conductive metal, such as Ag. As shown in Fig. 10, an electric feeding point of the radiation conductor 22 is connected with an inner conductor of the feeder cable 25. On the other hand, the first ground conductor 23 is connected with an outer conductor of the feeder cable 25.

[0034] The base plate 24 has a rectangular shape with an opening 24a, and is provided with internal-thread portions 24b at multiple positions. By fastening the setscrews 33 extending through corresponding projection tabs 30a of the frame body 30 to the corresponding internal-thread portions 24b, the frame body 30 is secured to the base plate 24. As shown in Fig. 10, the base plate 24 is fixed to the rear glass 51 with the moisture curing resin 34 and double-side adhesive tapes 35. The double-side adhesive tapes 35 function as temporarily fixing means while waiting for the moisture curing resin 34 to harden.

[0035] Referring to Fig. 11, the rectangular frame body 30 mainly includes a pair of side walls 30b, 30c facing each other, and a pair of side walls 30d, 30e facing each other. Opposite longitudinal ends of each of the side walls 30b, 30c are provided with the corresponding projection tabs 30a. A portion of the frame body 30 facing the rear glass 51 defines an engagement portion 30f that loosely fits in the opening 24a of the base plate 24. Four corners of the engagement portion 30f are provided with stoppers 30g. The stoppers 30g are placed on sections of the base plate 24 that are adjacent to the opening 24a. Thus, the stoppers 30g at the four corners of the engagement portion 30f abut on the base plate 24 such that the amount of insertion of the engagement portion 30f with respect to the opening 24a is set within the thickness of the base plate 24. Each of the side walls 30b, 30c is provided with a pair of the stoppers 30g respectively at opposite longitudinal ends thereof, such that each stopper 30g is projected slightly outward with respect to the adjacent side wall 30d or 30e. Furthermore, a portion of the frame body 30 opposite to the engagement portion 30f is provided with a plurality of small holes 30h.

[0036] Referring to Fig. 1A, since the rear glass 51 is a windowpane installed in the vehicle 50 at an angle with respect to the ground, when the frame body 30 is fixed to the rear glass 51 via the base plate 24, the side wall 30b defines a lower region disposed closer to the ground. Consequently, referring to Fig. 14, the side wall 30b is provided with two circular drainage holes 30i which allow an internal space to communicate with the external space. Furthermore, each of the side walls 30b to 30e of the frame body 30 is provided with tongue pieces 30j bent toward the internal space, and clearance holes 30k necessary for forming the corresponding tongue pieces 30j. The bent tongue pieces 30j support the circuit substrate 26. The drawings other than Fig. 11 illustrate a state where the tongue pieces 30j are not bent. The clearance holes 30k provided in the side wall 30b also function as drainage holes. The drainage holes 30i and the clearance holes 30k functioning also as drainage holes allow water droplets entering an internal space defined by the rear glass 51, the frame body 30, and the undersurface of the circuit substrate 26 (i.e. a radio-wave reflective surface 26b) to be drained outward quickly so as to prevent water from accumulating in the internal space.

[0037] As shown in Fig. 11, one surface of the circuit substrate 26 defines a component-holding surface 26a on which various types of electronic components (not shown) are mounted. Via a pair of connectors 36, 37, the component-holding surface 26a is connected to a second end portion of the feeder cable 25, whose first end portion is connected with the radiation conductor 22 and the first ground conductor 23. In other words, the second end portion of the feeder cable 25 is connected with an input section of a pre-amplifying circuit. Furthermore, the component-holding surface 26a has one end of each of the coaxial cable 28 and the DC cable 9 soldered thereto. The other end of the coaxial cable 28 has a connector 38 attached thereto. The peripheral region of the component-holding surface 26a is provided with a ground conductor (not shown), and is soldered to the frame body 30 at multiple positions. Accordingly, the frame body 30 electrically functions as a ground, and moreover, the circuit substrate 26 and the frame body 30 are mechanically joined with each other. The other surface (undersurface) of the circuit substrate 26 is provided with a second ground conductor composed of highly-conductive metal, such as Au, so as to constitute the radio-wave reflective surface 26b (see Fig. 13). The radio-wave reflective surface 26b faces the radiation conductor 22 and the first ground conductor 23 disposed on the rear glass 51, and is separated from the radiation conductor 22 and the first ground conductor 23 by a predetermined distance. The peripheral region of the radio-wave reflective surface 26b is supported by the tongue pieces 30j of the frame body 30 at multiple positions.

[0038] The cover 31 is provided with the opening 31a which is to be covered by the connector cover 32. Since the connector 37 faces the opening 31a, the connector 36 of the feeder cable 25 can be connected to the connector 37 of the circuit substrate 26 in a state where the frame body 30 holding the circuit substrate 26 is capped with the cover 31. The cover 31 is provided with bent segments 31b substantially around the entire peripheral region of the cover 31. The bent segments 31b fit around the side walls 30b to 30e of the frame body 30 and are provided with a plurality of engagement protrusions 31c that protrude inward. The engagement protrusions 31c are provided at positions corresponding to the small holes 30h of the frame body 30. The resilience of the bent segments 31b allows the engagement protrusions 31c to be press-fitted into the corresponding small holes 30h. Consequently, the cover 31 can be readily engaged to the frame body 30 in a snap-fit fashion. Since the circuit substrate 26 is installed in the frame body 30 before the engagement process of the cover 31, the installation process of the circuit substrate 26 is simplified.

[0039] When the frame body 30 capped with the cover 31 is fixed to the rear glass 51 via the base plate 24, a region of the cover 31 proximate the side wall 30b of the frame body 30 defines a lower region disposed closer to the ground. Consequently, the lower region of the cover 31 is provided with four rectangular drainage holes 31d. The drainage holes 31d allow water droplets entering an internal space defined by the component-holding surface 26a of the circuit substrate 26, the frame body 30, the cover 31, and the connector cover 32 to be drained outward quickly so as to prevent water from accumulating in the internal space.

[0040] An assembly process of the satellite antenna device 200 described above will now be described. Firstly, the radiation conductor 22 and the first ground conductor 23 are formed on the inner surface of the sheet of glass constituting the rear glass 51. The first end portion of the feeder cable 25 is then soldered to predetermined positions of the radiation conductor 22 and the first ground conductor 23. Secondly, the base plate 24 is securely fixed to the inner surface of the sheet of glass by using, for example, the moisture curing resin 34. The engagement portion 30f of the frame body 30 is then inserted into and positioned within the opening 24a. Subsequently, the frame body 30 is fixed to the internal-thread portions 24b of the base plate 24 via the setscrews 33. Here, the circuit substrate 26 is preliminarily installed in the frame body 30; the ends of the coaxial cable 28 and the DC cable 9 are preliminarily soldered on the circuit substrate 26; and the cover 31 is preliminarily engaged with the frame body 30. Moreover, when the frame body 30 is to be screwed onto the base plate 24, the feeder cable 25 is pulled toward the exterior of the frame body 30 via a clearance recess 30m (see Fig. 11) provided in the side wall 30d. Thirdly, after fixing the frame body 30 to the base plate 24, the connector 36 attached to the second end portion of the feeder cable 25 is connected to the connector 37 of the circuit substrate 26 facing the opening 31a of the cover 31. Subsequently, the connector cover 32 is mounted on the cover 31 so as to cover the opening 31a, whereby an attachment process for attaching the electronic circuit unit 21 to the sheet of glass constituting the rear glass 51 is completed.

[0041] The unique advantages of the above embodiment will be described below in detail. The unique advantages of the ground-based antenna device 100 will be described first. In detail, due to the fact that the connecting sections between the soldering sections 4a and the other sections of the base plate 4 are defined by the narrow sections 4e, these other sections of the base plate 4 do not receive much heat during the heating process for soldering the base plate 4 to the radiation conductor 2. Consequently, the soldering process can be completed within a small amount of time. Furthermore, each of the soldering sections 4a is provided with one of the protrusions 4c such that a solder-accumulation space is formed around the protrusion 4c. This prevents strength reduction caused by a lack of solder in the soldering sections 4a, whereby a highly reliable solder connection is achieved.

[0042] Furthermore, in the ground-based antenna device 100, the back surface of the reflector plate 3 is provided with the angle-maintaining member 15. Specifically, due to the fact that the contact edges 15a with high dimensional accuracy are in contact with the back surface of the reflector plate 3 and the flat surface of the base plate 4, the angle of inclination of the reflector plate 3 is set in a highly accurate manner with respect to the sheet of glass (rear glass) 51. Accordingly, a desired antenna performance can be achieved. Moreover, the angle-maintaining member 15 significantly improves the mechanical strength of the reflector plate 3, and thus reduces the possibility of the reflector plate 3 deforming into an undesired shape in response to receiving an external force during, for example, the assembly process. Accordingly, this further contributes to higher reliability in view of strength.

[0043] Furthermore, in the ground-based antenna device 100, the first end portion of the feeder cable 5 connected to the electric feeding points of the radiation conductor 2 is positioned by the supporting segments 4g and the sheet of glass (rear glass) 51 by being sandwiched therebetween, and moreover, the feeder cable 5 extending adjacent to the exterior of the housing 7 is positioned by the hook segment 4h and the supporting notch 11e. Accordingly, the feeder cable 5 can extend efficiently along a predetermined path.

[0044] Furthermore, in the ground-based antenna device 100, the coaxial cable 8 is held by the arm segment 10f extending from the frame body 10. This achieves a stable orientation of the coaxial cable 8 during the assembly process, and also prevents the connecting section of the coaxial cable 8 from being damaged in a case where a pulling force acts upon the coaxial cable 8. Moreover, by changing the metallic arm segment 10f into a desired shape, the orientation of the coaxial cable 8 can be readily corrected. Accordingly, the fixing process of the coaxial cable 8 can be performed in an extremely simple manner without using, for example, binders and adhesive tapes.

[0045] Furthermore, in the ground-based antenna device 100, the frame body 10 housing the circuit substrate 6 is screwed on the base plate 4 that is preliminarily fixed on the sheet of glass (rear glass) 51. This eliminates the need for performing complicated processes, such as demounting and remounting processes, when the circuit substrate 6 is to be inspected or replaced with a new one, and thus allows for easier maintenance.

[0046] Furthermore, in the ground-based antenna device 100, the frame body 10 and the cover 11 included in the housing 7 are respectively provided with the drainage holes 10i and the drainage holes 11d. Since the drainage holes 10i, 11d are provided at the bottommost portion of the electronic circuit unit 1 attached to the rear glass 51 that is disposed at an angle with respect to the ground, the component-holding surface 6a of the circuit substrate 6 is prevented from being immersed in water even when water droplets enter the internal space of the housing 7. Accordingly, a malfunction and failure caused by intrusion of water droplets are less likely to occur in the ground-based antenna device 100 such that high reliability is guaranteed over a long period of time.

[0047] Next, the unique advantages of the satellite antenna device 200 will be described. In detail, since the undersurface of the circuit substrate 26 constitutes the radio-wave reflective surface 26b that faces the radiation conductor 22 and the first ground conductor 23, a radio-wave emitted towards the interior of the vehicle 50 is reflected by the radio-wave reflective surface 26b so as to be emitted towards the exterior of the rear glass 51. Thus, a higher radiation gain can be attained in the incoming direction of a tuned radio-wave. Moreover, since the radio-wave reflective surface 26b (second ground conductor) defining the undersurface of the circuit substrate 26 also functions as a part of the first ground conductor 23, a total surface area required for the overall ground conductor can be attained by the total dimension of the radio-wave reflective surface 26b and the first ground conductor 23 on the rear glass 51. Consequently, this contributes to a size reduction of the first ground conductor 23 disposed on the inner surface of the rear glass 51. In view of the fact that the height of the radio-wave reflective surface 26b must be set accurately with respect to the radiation conductor 22 and the first ground conductor 23, since the frame body 30 housing the circuit substrate 26 according to the above embodiment is positioned properly in the planar direction of the base plate 24 via the engagement portion 30f and in the thickness direction of the base plate 24 via the stoppers 30g, the circuit substrate 26 is automatically disposed at a predetermined position when the frame body 30 is mounted onto the base plate 24. This means that the height of the circuit substrate 26 is set accurately with respect to the radiation conductor 22, and moreover, prevents an undesired gap from being formed between the frame body 30 and the base plate 24. In other words, since the electronic circuit unit 21 of the satellite antenna device 200 is an assembly structure in which the height of the radio-wave reflective surface 26b is set in a highly accurate manner, a high antenna performance is guaranteed. Moreover, since the frame body 30 can be fabricated easily due to having a simple structure, the dimensional accuracy of the engagement portion 30f and the stoppers 30g can be readily improved.

[0048] Furthermore, similar to the ground-based antenna device 100, the satellite antenna device 200 is advantageous in that the frame body 30 and the cover 31 included in the housing 27 are respectively provided with the drainage holes 30i and the clearance holes 30k, functioning also as drainage holes, and the drainage holes 31d. Since the drainage holes 30i, 31d and the clearance holes 30k are provided at the bottommost portion of the electronic circuit unit 21 attached to the rear glass 51 that is disposed at an angle with respect to the ground, the component-holding surface 26a and the radio-wave reflective surface 26b of the circuit substrate 26 are prevented from being immersed in water even when water droplets enter the internal space of the housing 27. Accordingly, a malfunction and failure caused by intrusion of water droplets are less likely to occur in the satellite antenna device 200 such that high reliability is guaranteed over a long period of time.

[0049] Furthermore, similar to the ground-based antenna device 100, the satellite antenna device 200 is advantageous in that the frame body 30 housing the circuit substrate 26 is screwed on the base plate 24 that is preliminarily fixed on the sheet of glass (rear glass) 51. This eliminates the need for performing complicated processes, such as demounting and remounting processes, when the circuit substrate 26 is to be inspected or replaced with a new one, and thus allows for easier maintenance.

[0050] Although the above embodiment describes an in-vehicle antenna apparatus in which the ground-based antenna device 100 and the satellite antenna device 200 are arranged in a side-by-side manner and operate in a mutually complementary manner, the present invention is not limited to such a structure. For example, the scope of the present invention may include an in-vehicle antenna apparatus provided with only one of the two antenna devices. Furthermore, the in-vehicle antenna apparatus may alternatively be mounted on, for example, the front glass of the vehicle instead of the rear glass.

Claims

1. An in-vehicle antenna apparatus comprising a sheet of glass serving as a windowpane installed in a vehicle; a patch-like radiation conductor disposed on an inner surface of the sheet of glass facing an inside of the vehicle; and a circuit substrate whose first surface is provided with an electric circuit connected to the radiation conductor,
wherein a second surface of the circuit substrate is provided with a second ground conductor for the electric circuit, the second ground conductor being opposed to and disposed separate from the radiation conductor and functioning as a radio-wave reflective surface.

2. The in-vehicle antenna apparatus according to Claim 1, wherein the inner surface of the sheet of glass is provided with a first frame-like ground conductor that surrounds the radiation conductor, wherein the electric circuit is connected with the radiation conductor and the first ground conductor, and wherein the second ground conductor is opposed to and disposed separate from the radiation conductor and the first ground conductor so as to function as the radio-wave reflective surface.

3. The in-vehicle antenna apparatus according to Claim 1 or 2, further comprising a base plate fixed on the inner surface of the sheet of glass; and a housing that houses the circuit substrate, wherein the housing is mounted on the inner surface of the sheet of glass via the base plate.

4. The in-vehicle antenna apparatus according to Claim 3, wherein the housing includes a sheet-metal frame body that surrounds and supports the circuit substrate and that is fixed to the base plate in a detachable manner; and a sheet-metal cover that engages with the frame body so as to cover the first surface of the circuit substrate.

Drawing